The present invention addresses a need to quickly find an accurate heading of a hand carried device without the need for magnetic field measurement associated with, for example, true north determinations. Portable systems capable of being carried by humans in a typical application desired by persons moving across country based on non-magnetic north (or south) seeking systems are not available due to a variety of limiting factors including size, weight, and power. Accordingly, in simplified terms, an invention has been created to provide a needed capability to determine a desired orientation of a sensor at a desired point with respect to the Earth (e.g., true north) based on determination of orientation of a reference axis of a sensor with respect to locations of multiple points and relationships between the multiple points with a significant degree of accuracy using non-magnetic directional sensing, orientation sensing, determinations via global positioning system (GPS), and a sequence of measurements along a displaced path. Location can include elevation of the sensor at each point of measurement which can be used in an embodiment. A desired orientation of the sensor at a desired point can include the first point at which a suitably accurate orientation, e.g., true north, can be determined e.g., less than five mil degrees accuracy (e.g., an angular mil can be found by dividing 360 degrees by 6400). A sequence of measurements can include at least two measurements in accordance with an embodiment of the invention along a path of travel which is, for example, not purely vertical in elevation. An embodiment of the non-magnetic directional sensing, navigational and orientation system can include an inertial navigation system coupled with a GPS system along with a control system adapted for executing a series of computations and generating results in accordance with an embodiment of the invention. Accordingly, multiple measurements and determinations can be made until a predetermined orientation accuracy value has been achieved.
Generally, an embodiment can include a navigation and location system is provided that can include an inertial measurement unit (IMU) comprising an in a strap down configuration and a GPS, and a control section that determines orientation of a range sensor aligned with one axis of the IMU with respect to the Earth based on a sequence of system orientation and location measurements from said IMU/GPS along a displaced path from a starting point to an activation point. Remote geo-location of the object can be determined based on determined range and bearing to the object determined by rotating axis of at least one reference frame from the strap down IMU axis with gravity and aligning another axis with a line of longitude through the displacement path to determine true north then determining an azimuth or bearing angle between true north and the range sensor output axis oriented on the object.
For example, an embodiment can provide a solution to meet unmet needs that includes, for simplification purposes, two parts. A first general part includes deriving a series of accurate location, elevation, and heading determinations via GPS. A second part includes accurately capturing an orientation of a sensing device in accordance with an embodiment of the invention and thus a direction that the non-magnetic sensor is pointing or orientated. An embodiment of the invention also includes a system adapted to execute the above parts in a variety of sequences to determine required information that is in turn used to identify with significant precision a needed geodetic or Earth fixed orientation.
An additional embodiment also is adapted to remote sensing of a specific location of a location of interest or object based on a combination of current navigation location/orientation and remote sensing of range/orientation to the location/object of interest. For example, an embodiment of the invention can provide a remote sensing/determination of position of an object/location of interest based on the non-magnetic based location/navigation/orientation determination capability. An example of remote sensing embodiments can include addition of a laser range finder (LRF) in addition to an additional set of computations in a control system in accordance with an embodiment of the invention. An exemplary embodiment can determine remotely coordinates of a location of interest (LoI) using such an embodiment.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.